1. Field of the Invention
The present invention relates to semiconductor manufacturing and, more specifically, to vacuum chucks for handling wafers during semiconductor manufacturing.
2. Description of Related Art
During the semiconductor chip manufacturing, a semiconductor wafer undergoes various processing to create a plurality of chips on the wafer. Additionally, in such various phases of the manufacturing the wafer, undergoes various inspection and quality checks to assure success of the production line. It is known in the art to use vacuum chucks to hold the wafer during the manufacturing, inspection and testing stages.
A conventional vacuum chuck generally comprises a flat plate having a support structure and provisions for delivering vacuum to the back side of the wafer in order to secure the wafer to the support structure. An exemplary conventional chuck 10 is shown in FIG. 1. It comprised substantially of a plate 20, having circular vacuum tunnels 30 having vacuum holes 40 at the bottom thereof. The wafer is placed on the surface of the plate 20, and is secured to the surface by the vacuum delivered to tunnels 30 via holes 40. the chuck is secured to a stage via holders 50. Examples of such chucks can be seen in U.S. Pat. Nos. 5,191,218 and 5,534,073.
The present inventors have identified certain disadvantages in the vacuum chuck of the prior art. First, it has been determined that the chuck can be a source for back-side contamination of the wafer. With the rapid reduction in design rules, the importance of previously irrelevant contaminants has been increasing, including backside contamination of the wafer.
Additionally, due to the cautious acceptance of 300 mm wafer processing by the industry, there may be a need to provide processing equipment capable of processing both 200 mm and 300 mm wafers. Such processing equipment would require chucks capable of handling both 200 mm and 300 mm wafers. Therefore, simply scaling the prior art chuck to accept 300 mm wafers may provide an inadequate solution for the industry.
The introduction of 300 mm wafer also raises the importance of the forces exerted by the chuck on the wafer. Specifically, because of the increased diameter, a warped chuck may cause warpage of the wafer, while a perfectly flat chuck may exert an unwanted pressure on slightly warped wafers.